120v. verses 208 on a lighting load?
- Thread starter electro1
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
It would be a good idea to break yourself of the habit of saying ?per phase,? when you speak of current. You never add the current from one phase to the current from another phase, to get the total current. Never. For this example (i.e., a single phase 208 volt load), you need to recognize that the current leaving the source on one phase will return to the source on the other phase. So it is the same current on both phases. They don?t add up, they are the same thing.
Think of it this way: Suppose you get pulled over by a police officer for being alone in the car while driving in a lane reserved for carpools. Do you think the police officer would accept the following explanation: ?But officer, I am in the car, and I am in the car, so that makes two of us in the car??
Think of it this way: Suppose you get pulled over by a police officer for being alone in the car while driving in a lane reserved for carpools. Do you think the police officer would accept the following explanation: ?But officer, I am in the car, and I am in the car, so that makes two of us in the car??
I don't know. I'll make a stab at itelectro1 said:
The load is what it is. No matter how you arrange it, it's still 3 - 400W lamps.electro1 said:
You left some information out, so I'm going to have to guess:electro1 said:
1. The 11A was with all three lamps connected to one 1phase 120V circuit (two wires, hot and neutral)
2. The lamps have multi-tap ballasts, likely 120V, 208V, 240V, 277V
3. With all three lamps connected to one 1phase 208V circuit (two hot wires), they draw 6.3A.
If any of this is wrong, then throw the rest out.
No. Current always forms a loop. What goes out, has to come back. The Mathematical way to say this is, "For any point, (Summation I) = 0 Or, the current entering the lamps equals the current leaving the lamps. So, The 6.8A entering one end of the lamps is the same current leaving the other end of the lamps.electro1 said:
If you want the apparent power delivered to the lamps, then one takes the current through the lamps (6.8A or 11A) times the voltage across the lamps (208V or 120V)
120V X 11A = 1320VA
208V X 6.8A = 1310VA
I would call that the same load.
carl
e57
Senior Member
- Location
- San Francisco, CA
charlie b said:
Another analogy would be.... "If I'm here, and you're here, dooesn't that make it OUR TIME?" Jeff Spickolli (Fast Times at Ridgemont High)
brian john
Senior Member
- Location
- Leesburg, VA
Charlie: How about this:
"But officer I am in the car now and this afternoon I Will be driving back in the other car pool (HOV* in Virginia) lanes. SO I add up RIGHT?, As he proceeds to write you a ticket"
HOV= High Occupancy Vehicles, I was told they changed the name from Car Pool at taxpayers expense (cost of signage) for some legalize issue someone tried to pull in court to avoid a fine
"But officer I am in the car now and this afternoon I Will be driving back in the other car pool (HOV* in Virginia) lanes. SO I add up RIGHT?, As he proceeds to write you a ticket"
HOV= High Occupancy Vehicles, I was told they changed the name from Car Pool at taxpayers expense (cost of signage) for some legalize issue someone tried to pull in court to avoid a fine
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I was specifically referring to a single phase, 208 volt load. That means there is no neutral wire involved. The current leaves the source on Phase A, goes through the load, and returns to the source on Phase B. An ammeter might tell you there is a five amp current on Phase A, and the same ammeter might tell you there is a five amp current on Phase B. You don?t add those two to get ten amps, because it is the same five amps being measured.kencoel said:
It is exactly the same thing as taking an ammeter measurement on a wire, then moving the ammeter two feet further down the same wire. You might get a five amp reading both times, but it is the same five amps.
ramdiesel3500
Senior Member
- Location
- Bloomington IN
I like to think of it like a cross cut saw. 120V is like a one-man saw where the speed and direction of the saw movement is similar to the amperage in a circuit. With a 2-man crosscut saw, the blade does not necessarily move any faster, but while one man is pushing the other is pulling so the force on the saw is twice as much and the work done by the saw is also twice as much.
brantmacga
Señor Member
- Location
- Georgia
- Occupation
- Former Child
"The Mathematical way to say this is, "For any point, (Summation I) = 0 Or, the current entering the lamps equals the current leaving the lamps."
This is called kirchoff's law.
This is called kirchoff's law.
- Status